The invention relates to a method of encoding, compatible with conventional television signals, an extended television signal comprising conventional television signal components and simultaneously at least one additional signal.
The invention further relates to an apparatus for decoding an extended television signal, encoded compatible with a conventional television signal, comprising conventional television signal components and simultaneously at least one additional signal, said apparatus comprising means for decoding of the at least one additional signal.
Several systems have already been proposed to improve existing composite television systems. In a number of these proposals, an additional signal is encoded in the high-frequency portion of the active video spectrum by means of an extended encoder circuit. The method with which this additional signal is encoded differs per system, but it always causes artifacts on display on a conventional or standard receiver as the receiver considers the additional signal as if it were a normal part of the video information, whereby crosstalk of the additional signal to both the luminance signals and the chrominance signals may occur in the standard receiver. This crosstalk results in brightness errors and/or color errors on a standard display screen.